Systems and methods for quick power delivery mode changes

ABSTRACT

According to one aspect, an uninterruptable power supply (UPS) is provided. The UPS includes a first input constructed to receive input power from a first power source, a second input constructed to receive input power from a second power source, an output constructed to provide output alternating current (AC) power derived from at least one of the first power source and the second power source, a bypass switch having an on state and an off state coupled between the first input and the output, an inverter coupled between the second input and the output and constructed to generate the output AC power. The UPS being constructed to quickly transition from a first power delivery mode that provides output power derived from the first power source to a second power delivery mode that provides output power derived from the second power source.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. National Stage Application under 35 U.S.C. §371 of International Application No. PCT/US2014/032932, filed Apr. 4,2014, titled SYSTEMS AND METHODS FOR QUICK POWER DELIVERY MODE CHANGES,which is hereby incorporated herein by reference in its entirety.

BACKGROUND

Technical Field

Embodiments of the present disclosure relate generally to quick powerdelivery mode changes. More specifically, embodiments relate to systemsand methods for quick power delivery mode changes in uninterruptablepower supplies (UPS).

Background Discussion

UPS's are generally used to isolate an external load from powerdisturbances including, for example, power surges, sags, glitches,blackouts, and brownouts. UPS's isolate an external load from powerdisturbances by deriving output power from multiple power sources. Inthe event that a power disturbance is detected from a first powersource, the UPS may derive output power from a separate second powersource.

SUMMARY

According to one aspect, a UPS is provided. The UPS comprises a firstinput constructed to receive input power from a first power source, asecond input constructed to receive input power from a second powersource, an output constructed to provide output alternating current (AC)power derived from at least one of the first power source and the secondpower source, a bypass switch having an on state and an off statecoupled between the first input and the output, an inverter coupledbetween the second input and the output and constructed to generate theoutput AC power based on inverter commands, and a controller coupled tothe inverter. The controller configured to detect a power failure of thefirst power source, disconnect the first input from the output at leastin part by changing the bypass switch from the on state to the off stateresponsive to detecting the power failure, and generate the invertercommands to output AC power derived from the second power source basedon an inverter reference signal responsive to detecting the powerfailure, the inverter reference signal being a non-sinusoidal voltagesignal for a first period of time and a sinusoidal voltage referenceafter the first period of time.

In one embodiment, the non-sinusoidal voltage reference is one of asquare wave, a pulse train, and a flat-top sinusoidal signal. In oneembodiment, the first period of time is between 1 and 1.5 power cycles.

In one embodiment, the UPS further comprises an inverter switch havingan on state and an off state coupled between the inverter and theoutput. In this embodiment, controller may be coupled to the inverterswitch and further configured to connect the inverter to the output atleast in part by changing the state of the inverter switch from the offstate to the on state.

In one embodiment, the bypass relay switch comprises a first terminalcoupled to the first input, a second terminal coupled to the output, afirst power source terminal constructed to receive power at a firstvoltage level, a second power source terminal constructed to receivepower at a second voltage level, the second voltage level being lowerthan the first voltage level, a movable armature coupled between thefirst port and the second port, the movable armature having a firststate that connects the first terminal to the second terminal and asecond state that disconnects the first terminal from the secondterminal, a circuit coupled to the first power source terminal and tothe second power source terminal, the circuit constructed to induce acoil to create a first magnetic field of a first strength to move themoveable armature from the first state to the second state by applyingthe first voltage level to the coil and to induce the coil to create asecond magnetic field of a second strength to maintain the movablearmature in the second position by applying the second voltage level tothe coil, the second strength being weaker than the first strength, anda spring coupled to the moveable armature, the spring constructed tohold the moveable armature in the first state against an opposingmagnetic field of the second strength. The UPS may further comprise adirect current (DC) bus coupled to the inverter and wherein the DC bushas a voltage level substantially equal to the first voltage at thefirst power terminal of the bypass relay switch. The coil may have avoltage rating substantially equal to the second voltage level at thesecond terminal of the bypass relay switch.

In one embodiment, the circuit of the bypass switch includes a firstdiode coupled between the first power source terminal and the coil and asecond diode coupled between the second power source terminal and thecoil. The circuit of the bypass switch may further include a resistorcoupled between the first diode and the first power source terminal.

According to one aspect, a method for operating a UPS is provided. Themethod comprises receiving input power from a first power source,providing output power to an external load based on the input power fromthe first power source, detecting a power failure of the first powersource, disconnecting the first power source from the external loadresponsive to detecting the power failure of the first power source,receiving input power from a second power source, generating invertercommands based on an inverter reference signal, and generating outputalternating current (AC) power derived from the second power sourcebased on the inverter commands. The act of generating inverter commandsincludes generating a non-sinusoidal inverter voltage reference signalfor a first period of time and generating a sinusoidal inverter voltagereference signal after the first period of time.

In one embodiment, generating the non-sinusoidal reference voltagesignal includes generating one of a square wave, a pulse train, and aflat-top sinusoidal signal. In one embodiment, the first period of timeis between 1 and 1.5 power cycles.

In one embodiment, disconnecting the first power source from theexternal load includes changing a bypass switch coupled between thefirst power source and the external load from an on state to an offstate. In this embodiment, changing the bypass switch from the on stateto the off state may include moving a moveable armature of theelectromagnetic relay from a closed state first state to an open stateby a spring coupled to the movable armature. The bypass switch mayfurther include a coil having a voltage rating and wherein the spring isconstructed to hold the moveable armature in the open state against anopposing magnetic field generated by applying a voltage level equal tothe voltage rating to the coil.

In one embodiment, generating inverter commands includes generatingpulse width modulation (PWM) commands.

According to one aspect, a UPS is provided. The UPS comprises a firstinput constructed to receive input power from a first power source, asecond input constructed to receive input power from a second powersource, an output constructed to provide output alternating current (AC)power derived from at least one of the first power source and the secondpower source, a bypass switch having an on state and an off statecoupled between the first input and the output, an inverter coupledbetween the second input and the output and constructed to generate theoutput AC power, and means for transitioning the UPS from a first powerdelivery mode that provides output power derived from the first powersource to a second power delivery mode that provides output powerderived from the second power source.

In one embodiment, the means for transitioning the UPS from the firstpower delivery mode to the second power delivery modes includes a meansfor reducing a period of time required for the bypass switch to changefrom the on state to the off state.

In one embodiment, the means for transitioning the UPS from the firstpower delivery mode to the second power delivery mode includes a meansfor quickly providing output power from the inverter in the second powerdelivery mode.

Still other aspects, embodiments, and advantages of these exemplaryaspects and embodiments, are discussed in detail below. Moreover, it isto be understood that both the foregoing information and the followingdetailed description are merely illustrative examples of various aspectsand embodiments, and are intended to provide an overview or frameworkfor understanding the nature and character of the claimed subjectmatter. Particular references to examples and embodiments, such as “anembodiment,” “another embodiment,” “some embodiments,” “otherembodiments,” “an alternate embodiment,” “various embodiments,” “oneembodiment,” “at least one embodiments,” “this and other embodiments” orthe like, are not necessarily mutually exclusive and are intended toindicate that a particular feature, structure, or characteristicdescribed in connection with the embodiment or example and may beincluded in that embodiment or example and other embodiments orexamples. The appearances of such terms herein are not necessarily allreferring to the same embodiment or example.

Furthermore, in the event of inconsistent usages of terms between thisdocument and documents incorporated herein by reference, the term usagein the incorporated references is supplementary to that of thisdocument; for irreconcilable inconsistencies, the term usage in thisdocument controls. In addition, the accompanying drawings are includedto provide illustration and a further understanding of the variousaspects and embodiments, and are incorporated in and constitute a partof this specification. The drawings, together with the remainder of thespecification, serve to explain principles and operations of thedescribed and claimed aspects and embodiments.

BRIEF DESCRIPTION OF DRAWINGS

Various aspects of at least one embodiment are discussed below withreference to the accompanying figures, which are not intended to bedrawn to scale. The figures are included to provide an illustration anda further understanding of the various aspects and embodiments, and areincorporated in and constitute a part of this specification, but are notintended as a definition of the limits of any particular embodiment. Thedrawings, together with the remainder of the specification, serve toexplain principles and operations of the described and claimed aspectsand embodiments. In the figures, each identical or nearly identicalcomponent that is illustrated in various figures is represented by alike numeral. For purposes of clarity, not every component may belabeled in every figure. In the figures:

FIG. 1 illustrates a block diagram of a UPS in accordance with oneembodiment;

FIG. 2 illustrates one embodiment of an electromagnetic relay;

FIG. 3 illustrates a block diagram, of a UPS controller in accordancewith one embodiment;

FIG. 4 is a graph illustrating various UPS waveforms;

FIG. 5 is a flow diagram of one example quick power delivery mode changemethod;

FIG. 6 is a flow diagram of one example method of generating invertercommands; and

FIG. 7 is a block diagram of one example of a computer system upon whichvarious aspects of the present embodiments may be implemented.

DETAILED DESCRIPTION

Examples of the methods and systems discussed herein are not limited inapplication to the details of construction and the arrangement ofcomponents set forth in the following description or illustrated in theaccompanying drawings. The methods and systems are capable ofimplementation in other embodiments and of being practiced or of beingcarried out in various ways. Examples of specific implementations areprovided herein for illustrative purposes only and are not intended tobe limiting. In particular, acts, components, elements and featuresdiscussed in connection with any one or more examples are not intendedto be excluded from a similar role in any other examples.

Also, the phraseology and terminology used herein is for the purpose ofdescription and should not be regarded as limiting. Any references toexamples, embodiments, components, elements or acts of the systems andmethods herein referred to in the singular may also embrace embodimentsincluding a plurality, and any references in plural to any embodiment,component, element or act herein may also embrace embodiments includingonly a singularity. References in the singular or plural form are notintended to limit the presently disclosed systems or methods, theircomponents, acts, or elements. The use herein of “including,”“comprising,” “having,” “containing,” “involving,” and variationsthereof is meant to encompass the items listed thereafter andequivalents thereof as well as additional items. References to “or” maybe construed as inclusive so that any terms described using “or” mayindicate any of a single, more than one, and all of the described terms.In addition, in the event of inconsistent usages of terms between thisdocument and documents incorporated herein by reference, the term usagein the incorporated references is supplementary to that of thisdocument; for irreconcilable inconsistencies, the term usage in thisdocument controls.

As described above, UPS's isolate a load from power disturbances byproviding output power to a load derived from various power sources. Theload, however, may be starved of power during a switching processperformed by the UPS to transition from a first mode delivering outputpower from a first power source to a second mode delivering output powerfrom a second power source. Aspects of the current disclosure relate toUPS's with quick power delivery mode changeover capabilities to reducethe time required to change power delivery modes.

In one embodiment, a UPS employs a bypass relay with a mechanicaloverdrive that controls the connection between a first power source andan external load. In this embodiment, the bypass relay with a mechanicaloverdrive employs an overrated spring that reduces the time required forthe relay to change state and thereby reduce the time required totransition from providing output power from the first power source toproviding output power from another power source.

In one embodiment, the UPS is constructed to transition from a firstmode delivering alternating current (AC) power from a first AC powersource to a second mode delivering AC power from a second direct current(DC) power source. In this embodiment, the UPS includes an invertercoupled between the second DC power source and the AC external load. TheUPS inverter generates output power responsive to received invertercommands generated by, for example, a controller of the UPS. Thecontroller generates the inverter commands based on an inverter voltagereference signal that may be constructed to be a non-sinusoidal wave fora first period of time. The initial non-sinusoidal wave maximizes theamount of current supplied to the external load by the inverterimmediately after the external load is coupled to the inverter. Afterthe first period is complete, the UPS may generate a sinusoidal inverterreference signal. An example UPS 100 is described below with referenceto FIG. 1.

Example UPS

FIG. 1 illustrates an example online UPS 100 constructed to receivepower from an external source and provide output power to a load. TheUPS 100 includes an input 102, an output 104, a bypass switch 110, anAC/DC rectifier 106, a DC bus 120, a DC/AC inverter 108, a batterycharger 112, a battery 114, a DC/DC converter 116, a controller 118, andan inverter switch 122.

The input 102 is constructed to receive power from an external AC powersource such as a utility power source. The input 102 is selectivelycoupled to the AC/DC rectifier 106 that converts the input AC power toDC power. The input 102 is also selectively coupled to the output 104via the bypass switch 110. The output 104 is constructed to output ACpower to a load. The UPS may be constructed to receive via input 102 andoutput via output 104 single-phase AC power or three-phase AC power.

The AC/DC rectifier 106 is also coupled to the DC/AC inverter 108 viathe DC bus 120. The battery 114 is coupled to the DC bus 120 via thebattery charger 112 and also to the DC bus 120 via the DC/DC converter116. The DC/AC inverter 108 is selectively coupled to the output 104 viathe inverter switch 122. The controller 118 is coupled to the AC/DCrectifier 106, the DC/AC inverter 108, the bypass switch 110, thebattery charger 112, the DC/DC converter 116, and the inverter switch122. In other embodiments, the battery 114 and the charger 112 may becoupled to the AC/DC rectifier 106.

In one embodiment, the UPS 100 is configured to operate in one or moremodes of operation based on the quality of the AC power received fromthe utility source. In this embodiment, the controller 118 monitors theAC power received from the utility source at the input 102 and, based onthe monitored AC power, sends control signals to the bypass switch 110,the battery charger 112, the AC/DC rectifier 106, the DC/AC inverter108, the DC/DC converter 116, and the inverter switch 122 to controloperation of the UPS 100. The UPS modes of operation may include, forexample, a bypass mode, an online mode, and a battery mode. In onlinemode, the bypass switch 110 is off, the inverter switch is on, and theinput power received at the input 102 is rectified in the AC/DCrectifier 106 and inverted in DC/AC inverter 108 before reaching theoutput 104. A portion of the power received at the input port may beused to charge the battery 114 via the charger 112.

In battery mode, the UPS 100 draws power from the battery 114 via theDC/DC converter 116 to supplement and/or replace the power received atthe input 102. In bypass mode, the UPS 100 directly couples the input102 to the output 104 via the bypass switch 110 and disconnects theDC/AC inverter 108 via inverter switch 122.

One or more processes may be performed by the controller 118 to switchbetween various modes to minimize the probability of starving the loadof power while switching modes. Example processes performed by thecontroller 118 during a changeover from bypass mode to battery mode isdescribed below with reference to FIGS. 5-6. In addition to specializedprocesses performed by the controller 118, the bypass switch 110 may beemployed with a mechanical overdrive to reduce the time required tochange state. An example electromagnetic relay with a mechanicaloverdrive to reduce one of the opening time and the closing time thatmay be employed as bypass switch 110 is described below with referenceto FIG. 2.

Example Electromagnetic Relay

FIG. 2 illustrates an embodiment of an electromagnetic relay 200 with amechanical overdrive that may be employed as the bypass switch 110described above with reference to FIG. 1. The electromagnetic relay 200includes a first port 202, a second port 204, a spring 206, a movablearmature 208, a ground port 226, a first power port 228, a second powerport 230, and a relay drive circuit 210 including a coil 212 thatcreates a magnetic field 214, a switch 216, diodes 218 and 220, aresistor 222, and a capacitor 224.

In one embodiment, the electromagnetic relay 200 controls a connectionbetween the first port 202 and the second port 204. The state of therelay 200 is governed by the position of the movable armature 208. Themovable armature 208 is held in an open state by spring 206. Theelectromagnetic relay 200 employs a magnetic field (e.g., magnetic field214) to move the movable armature 208 from the open state to a closedstate that connects the first port 202 with the second port 204.

The relay drive circuit 210 controls the position of the movablearmature 208 responsive to, for example, a received control signal fromcontroller 118. The received control signal may control a state of theswitch 216. Closing the switch 216 induces a current in coil 212 thatcreates a magnetic field 214. The magnetic field 214 attracts themovable armature 208 to create a connection between the first port 202and the second port 204. Opening the switch 216 disconnects the coil 212from an external power source thereby causing the magnetic field 214 todecay. As the magnetic field 214 decays, the spring 206 pulls themovable armature 208 back to an open state that disconnects the firstport 202 from the second port 204. An example switch 216 includes, butis not limited to, an insulated-gate bipolar transistor (IGBT), ametal-oxide semiconductor field-effect transistor (MOSFET), or asilicon-controlled rectifier (SCR).

The first power source terminal 228 is constructed to receive power at afirst voltage level (e.g., 12 Volts), the coil 212 is rated to withstandthe first voltage level, and the second power source terminal 230 isconstructed to receive power at a second voltage level (e.g., 395 Volts)that is higher than the first voltage level. The second voltage levelmay be substantially the same as the voltage level of a DC bus of theUPS (e.g., DC bus 120 of UPS 100). In this embodiment, the voltageacross the coil 212 immediately after the switch 216 closes is similarto the second voltage level and substantially beyond a rated voltage ofthe coil 212. As the coil 212 generates magnetic field 214, the voltageacross the coil 212 drops to a voltage level at or below the firstvoltage level. The voltage level across the coil 212 may drop as thecurrent through the inductor increases because the resistor 222minimizes the amount of current available to the coil 212 from thesecond power source terminal 230. The resistance of resistor 222 may be,for example, 100,000 Ohms. The high voltage initially applied to thecoil 212 temporarily creates a strong magnetic field to initially movethe movable armature 208 from an open state to the closed state at anexpedited rate. After the voltage across the coil drops, a weakermagnetic field is generated that holds the movable armature 208 in theclosed position.

The electromagnetic relay 200 may further include a mechanical overdriveto expedite the rate at which the electromagnetic relay opens. Themechanical overdrive may include a spring with a high force constantthat reduces the time required for the moveable armature from the closedstate to the open state. The force constant of the spring may besufficiently high that the magnetic field 214 induced by the coil 212when only the lower first voltage level is applied is insufficient tomove the moveable armature from the open state to the closed state. Themagnetic field 214 induced by the coil 212 when the lower first voltagelevel is applied, however, may be sufficient to hold the movablearmature in the closed position.

In one embodiment, the coil 212 has a voltage rating of 24 Volts and thestrength of the magnetic field generated by applying 24 Volts to thecoil 212 is sufficient to move the moveable armature from an open stateto a closed state. In this embodiment, the spring requires 4.5milliseconds to move the movable armature from the closed position tothe open position after the coil 212 is disconnected from a powersource. In one example, a mechanical overdrive is added thatnecessitates a voltage of at least 31 Volts be applied to the coil 212in order to create a sufficiently strong magnetic field to initiallymove the movable armature from the open state to the closed state. Thisexample mechanical overdrive reduces the time required to move themoveable armature from the closed state to the open state from 4.5milliseconds to 3.3 milliseconds. In another example, a mechanicaloverdrive is added that necessitates a voltage of at least 46 Volts beapplied to the coil 212 in order to create a sufficiently strongmagnetic field to initially move the movable armature from the openstate to the closed state. This example mechanical overdrive reduces thetime required to move the moveable armature from the closed state to theopen state from 4.5 milliseconds to 2.36 milliseconds.

The construction of the electromagnetic relay 200 is not limited to thenormally-open construction illustrated in FIG. 2 where the spring 206 isfitted to keep the relay in an open state when switch 216 is open. Theelectromagnetic relay 200 may be constructed as a normally-closed relaywhere the spring 206 is fitted to keep the relay in a closed state whenswitch 216 is open. The state of the switch 216 may be controlled via aUPS controller (e.g., controller 118). An example UPS controller isdescribed below with reference to FIG. 3.

Example UPS Controller

In at least one embodiment, the controller 118 is configured to expeditethe transition between power delivery modes of the UPS 100. FIG. 3illustrates an example controller 300 for a UPS (e.g., controller 118for UPS 100) configured to quickly transition from a first powerdelivery mode to a second power delivery mode. The controller 300outputs Pulse Width Modulation (PWM) commands 312 to an inverter (e.g.,DC/AC inverter 108) based on a received inverter output voltage level316 and a received inverter output current level 314. The controller 300determines the PWM commands through a voltage reference generator module302, a voltage compensator module 304, a current compensator module 306,and difference modules 308 and 310.

In one embodiment, the received inverter output voltage 316 issubtracted from a voltage reference signal generated by the voltagegenerator module 302 in difference module 308 to produce an errorvoltage. The error voltage is provided to a voltage compensator 304 thatis constructed to generate a current signal based on the received errorvoltage. The received inverter output current 314 is subtracted from thecurrent signal output by the voltage compensator module 304 indifference module 310 to produce an error current. The error currentsignal is provided to current compensator module 306 that is constructedto generate PWM commands 312 for the inverter (e.g., DC/AC inverter108). The PWM commands 312 may direct one or more switching devices inthe inverter to generate the desired output inverter waveform.

In some embodiments, the voltage reference generator module 302generates a modified voltage reference signal to increase the amount ofpower immediately available to an external load after connecting theinverter to the external load. For example, the voltage referencegenerator 302 may generate a non-sinusoidal voltage reference signal fora first period of time immediately after a power delivery mode changeand generate a sinusoidal voltage reference signal after the firstperiod of time. FIG. 4 is a graph illustrating various UPS waveforms 400produced by employing a modified voltage reference signal. The UPSwaveforms 400 include an output current waveform 402, an invertervoltage reference waveform 404, and an output voltage waveform 406plotted against time during a power failure event 408 and an inverterturn-on event 410.

The output current waveform 402 illustrates the current supplied to aload coupled to the UPS. The output current waveform 402 and the outputvoltage waveform 406 prior to the power failure event 402 may beprovided from an external AC power source (e.g., a power grid) coupleddirectly to the output via a bypass switch (e.g., bypass switch 110 inFIG. 1). The output current waveform 402 and the output voltage waveform406 drop to zero directly after the power failure event 408. The UPS mayopen the bypass switch to disconnect the failed power source from theload and/or close a switch between an inverter (e.g., inverter switch122) and the load in the time interval between the power failure event408 and the inverter on event 410.

The inverter voltage reference waveform 404 is generated by the UPS(e.g., controller 118 of UPS 100) after the inverter turn-on event 410.The inverter voltage reference waveform 404 is a square wave for thefirst 2.5 power cycles before changing into a sinusoidal referencesignal. For example, the line frequency may be 50 Hz and the invertervoltage reference waveform 404 may be a square wave for 50 milliseconds(i.e., 20 milliseconds per cycle*2.5 power cycles). In another example,the line frequency may be 60 Hz and the inverter voltage referencewaveform 404 may be a square wave for approximately 41.5 milliseconds(i.e., approximately 16.6 milliseconds per cycle*2.5 power cycles).Employing a square wave for the first 2.5 cycles after the inverter turnon event 410 immediately provides power to the load as illustrated bythe output current waveform 402 and the output voltage waveform 406.Other non-sinusoidal waveforms may be employed including, for example, asinusoidal signal combined with pulse signals at the zero crossings, aflat-top sinusoidal signal, a pulse train, or any other signal thatminimizes the zero crossing. In addition, the period of time that theinverter voltage reference is a non-sinusoidal signal is not limited to2.5 cycles. For example, the duration of the non-sinusoidal referencesignal may be between 1 and 1.5 cycles.

In some embodiments, the components described above with regard to FIG.3 are software components that are executable by the controller 300. Inother embodiments, some or all of the components may be implemented inhardware or a combination of hardware and software. Controller 300 maytake a variety of forms dependent upon the specific application andprocesses used to perform the harmonic suppression. Example quickchangeover processes are described below with reference to FIGS. 5-6that may be executed by controller 300 or any computer systemcommunicatively connected to the UPS such as the computer systemdescribed below with reference to FIG. 7.

Example Power Delivery Mode Change Processes

As described above with reference to FIGS. 1 and 3, several embodimentsinclude controllers that perform processes which reduce the timerequired for a UPS to change from a first power delivery mode to asecond power delivery mode. In some embodiments, these quick powerdelivery mode change processes are executed by a microprocessor-basedcomputer system, such as the controller 118 in the UPS 100 describedabove with reference to FIG. 1 or the computer system 700 describedbelow with reference to FIG. 7. FIG. 5 illustrates one example powerdelivery mode change process 500 performed by a UPS 100 (e.g., executedby controller 118 of UPS 100). The power delivery mode change process500 may be performed after the UPS 100 experiences a power failure of afirst power source. The power delivery mode change process 500 begins inact 502.

In act 502, the UPS 100 disconnects the first power source from theload. Disconnecting the first power source from the load may includetransmitting a control signal to a switch (e.g., bypass switch 110)coupled between the first power source and the output. In act 504, theUPS 100 connects a second power source to the load. Connecting thesecond power source to the load may include transmitting a controlsignal to a switch (e.g., inverter switch 122) between the second powersource (e.g., battery 114) and the output.

In act 506, the UPS 100 generates inverter commands. The invertercommands may include one or more switching commands to the inverter tocause the inverter to output AC power. The act 506 is described furtherbelow with reference to the example inverter command generation process600 illustrated in FIG. 6. The inverter command generation process 600begins in act 602.

In act 602, the UPS 100 generates a non-sinusoidal inverter voltagereference as described above with reference to FIG. 4. Thenon-sinusoidal inverter voltage reference signal includes, for example,one of or a combination of a square wave, a pulse train, and a flat-topsinusoidal signal. In act 604, the UPS 100 generates PWM commands basedon the non-sinusoidal inverter voltage reference signal. The PWMcommands may be transmitted to one or more switches in the inverter(e.g., DC/AC inverter 108) to cause the inverter to output AC power tothe external load.

In act 606, the UPS 100 determines whether the startup phase iscomplete. The UPS 100 may determine whether the startup phase iscomplete based on a number of power cycles and/or a predetermined periodof time including, for example, a period of time between 1 and 1.5 powercycles. If the UPS 100 determines that the startup phase is complete,the UPS 100 proceeds to act 608 where the UPS 100 generates a sinusoidalvoltage reference and act 610 where the UPS 100 generates PWM commandsbased on the sinusoidal voltage reference. Otherwise, the UPS 100returns to act 602 and continues to generate the non-sinusoidal invertervoltage reference signal.

Embodiments of the quick power delivery mode change techniques have beendescribed for use in an online UPS 100 as shown in FIG. 1. In otherembodiments, the quick power delivery mode change techniques may beprovided in other types of UPSs including, for example, off-line,line-interactive, or any other type of UPS. The quick power deliverymode techniques may also be used in other types of power devicesincluding, for example, any power device that switches between two ormore power delivery modes.

In one example, the UPS may employ a bypass relay with a mechanicaloverdrive that controls the connection between a first power source andan external load to expedite the transition between two or more powerdelivery modes. In this example, the bypass relay with a mechanicaloverdrive employs an overrated spring that reduces the time required forthe relay to change state and thereby reduce the time required totransition from providing output power from the first power source toproviding output power from another power source. Alternatively or inconjunction with the bypass relay with the mechanical overdrive, the UPSmay employ a non-sinusoidal wave for a first period of time as aninverter voltage reference to maximize the amount of current supplied tothe external load by the inverter immediately after the external load iscoupled to the inverter.

Furthermore, various aspects and functions described herein in accordwith the present disclosure may be implemented as hardware, software,firmware or any combination thereof. Aspects in accord with the presentdisclosure may be implemented within methods, acts, systems, systemelements and components using a variety of hardware, software orfirmware configurations. Furthermore, aspects in accord with the presentdisclosure may be implemented as specially-programmed hardware and/orsoftware.

Example Computer System

FIG. 7 illustrates an example block diagram of computing componentsforming a system 700 which may be configured to implement one or moreaspects disclosed herein. For example, the system 700 may becommunicatively coupled to a UPS or included within a UPS and configuredto perform quick power delivery mode change processes as described abovewith reference to FIGS. 5-6.

The system 700 may include for example a general-purpose computingplatform such as those based on Intel PENTIUM-type processor, MotorolaPowerPC, Sun UltraSPARC, Texas Instruments-DSP, Hewlett-Packard PA-RISCprocessors, or any other type of processor. System 700 may includespecially-programmed, special-purpose hardware, for example, anapplication-specific integrated circuit (ASIC). Various aspects of thepresent disclosure may be implemented as specialized software executingon the system 700 such as that shown in FIG. 7.

The system 700 may include a processor/ASIC 706 connected to one or morememory devices 710, such as a disk drive, memory, flash memory or otherdevice for storing data. Memory 710 may be used for storing programs anddata during operation of the system 700. Components of the computersystem 700 may be coupled by an interconnection mechanism 708, which mayinclude one or more buses (e.g., between components that are integratedwithin a same machine) and/or a network (e.g., between components thatreside on separate machines). The interconnection mechanism 708 enablescommunications (e.g., data, instructions) to be exchanged betweencomponents of the system 700. Further, in some embodiments theinterconnection mechanism 708 may be disconnected during servicing of aPDU.

The system 700 also includes one or more input devices 704, which mayinclude for example, a keyboard or a touch screen. An input device maybe used for example to configure the measurement system or to provideinput parameters. The system 700 includes one or more output devices702, which may include for example a display. In addition, the computersystem 700 may contain one or more interfaces (not shown) that mayconnect the computer system 700 to a communication network, in additionor as an alternative to the interconnection mechanism 708.

The system 700 may include a storage system 712, which may include acomputer readable and/or writeable nonvolatile medium in which signalsmay be stored to provide a program to be executed by the processor or toprovide information stored on or in the medium to be processed by theprogram. The medium may, for example, be a disk or flash memory and insome examples may include RAM or other non-volatile memory such asEEPROM. In some embodiments, the processor may cause data to be readfrom the nonvolatile medium into another memory 710 that allows forfaster access to the information by the processor/ASIC than does themedium. This memory 710 may be a volatile, random access memory such asa dynamic random access memory (DRAM) or static memory (SRAM). It may belocated in storage system 712 or in memory system 710. The processor 706may manipulate the data within the integrated circuit memory 710 andthen copy the data to the storage 712 after processing is completed. Avariety of mechanisms are known for managing data movement betweenstorage 712 and the integrated circuit memory element 710, and thedisclosure is not limited thereto. The disclosure is not limited to aparticular memory system 710 or a storage system 712.

The system 700 may include a general-purpose computer platform that isprogrammable using a high-level computer programming language. Thesystem 700 may be also implemented using specially programmed, specialpurpose hardware, e.g. an ASIC. The system 700 may include a processor706, which may be a commercially available processor such as thewell-known Pentium class processor available from the Intel Corporation.Many other processors are available. The processor 706 may execute anoperating system which may be, for example, a Windows operating systemavailable from the Microsoft Corporation, MAC OS System X available fromApple Computer, the Solaris Operating System available from SunMicrosystems, or UNIX and/or LINUX available from various sources. Manyother operating systems may be used.

The processor and operating system together may form a computer platformfor which application programs in high-level programming languages maybe written. It should be understood that the disclosure is not limitedto a particular computer system platform, processor, operating system,or network. Also, it should be apparent to those skilled in the art thatthe present disclosure is not limited to a specific programming languageor computer system. Further, it should be appreciated that otherappropriate programming languages and other appropriate computer systemscould also be used.

Having thus described several aspects of at least one example, it is tobe appreciated that various alterations, modifications, and improvementswill readily occur to those skilled in the art. For instance, examplesdisclosed herein may also be used in other contexts. Such alterations,modifications, and improvements are intended to be part of thisdisclosure, and are intended to be within the scope of the examplesdiscussed herein. Accordingly, the foregoing description and drawingsare by way of example only.

What is claimed is:
 1. An uninterruptable power supply (UPS) comprising:an input constructed to receive input power; an output to provide outputalternating current (AC) power; a bypass switch having an on state andan off state coupled between the input and the output; an invertercoupled to the output and constructed to generate the output AC powerbased on inverter commands; and a controller coupled to the inverter,the input, and the bypass switch, and configured to: detect a powerfailure of the input power; disconnect the input from the output atleast in part by changing the bypass switch from the on state to the offstate responsive to detecting the power failure; and generate theinverter commands and provide the inverter commands to the inverter tooutput, by the inverter, the AC power based on an inverter referencesignal responsive to detecting the power failure, the inverter referencesignal having a non-sinusoidal voltage waveform for a first period oftime and a sinusoidal voltage waveform after the first period of time.2. The UPS of claim 1, wherein the non-sinusoidal voltage waveform isone of a square wave, a pulse train, and a flat-top sinusoidal signal.3. The UPS of claim 1, wherein the first period of time is between 1 and1.5 power cycles of the output AC power.
 4. The UPS of claim 1, furthercomprising an inverter switch having an on state and an off statecoupled between the inverter and the output.
 5. The UPS of claim 4,wherein the controller is coupled to the inverter switch and thecontroller is further configured to connect the inverter to the output,at least in part by changing the state of the inverter switch from theoff state to the on state.
 6. The UPS of claim 1, wherein the bypassswitch comprises: a first terminal coupled to the first input; a secondterminal coupled to the output; a first power source terminalconstructed to receive power at a first voltage level; a second powersource terminal constructed to receive power at a second voltage level,the second voltage level being lower than the first voltage level; amovable armature coupled between the first terminal and the secondterminal, the movable armature having a first state that connects thefirst terminal to the second terminal and a second state thatdisconnects the first terminal from the second terminal; a circuitcoupled to the first power source terminal and to the second powersource terminal, the circuit constructed to induce a first magneticfield of a first strength in a coil to move the moveable armature fromthe first state to the second state by applying the first voltage levelto the coil and to induce a second magnetic field of a second strengthin the coil to maintain the movable armature in the second position byapplying the second voltage level to the coil, the second strength beingweaker than the first strength; and a spring coupled to the moveablearmature, the spring constructed to hold the moveable armature in thefirst state against an opposing magnetic field of the second strength.7. The UPS of claim 6, further comprising a direct current (DC) buscoupled to the inverter and wherein the DC bus has a voltage levelsubstantially equal to the first voltage at the first power terminal ofthe bypass switch.
 8. The UPS of claim 6, wherein the coil has a voltagerating substantially equal to the second voltage level at the secondterminal of the bypass switch.
 9. The UPS of claim 6, wherein thecircuit includes a first diode coupled between the first power sourceterminal and the coil and a second diode coupled between the secondpower source terminal and the coil.
 10. The UPS of claim 9, wherein thecircuit further includes a resistor coupled between the first diode andthe first power source terminal.
 11. A method for operating anuninterruptable power supply (UPS), the method comprising: receivinginput power from a first power source; providing output power to anexternal load based on the input power from the first power source;detecting a power failure of the first power source; disconnecting thefirst power source from the external load responsive to detecting thepower failure of the first power source; receiving input power from asecond power source; generating an inverter voltage reference signalhaving a non-sinusoidal voltage waveform for a first period of time andhaving a sinusoidal voltage waveform after the first period of time;generating inverter commands based on the inverter voltage referencesignal; and generating output alternating current (AC) power derivedfrom the second power source based on the inverter commands.
 12. Themethod of claim 11, wherein generating the inverter voltage referencesignal having the non-sinusoidal voltage waveform includes generatingone of a square wave, a pulse train, and a flat-top sinusoidal signal.13. The method of claim 11, wherein the first period of time is between1 and 1.5 power cycles of the output AC power.
 14. The method of claim11, wherein disconnecting the first power source from the external loadincludes changing a bypass switch coupled between the first power sourceand the external load from an on state to an off state.
 15. The methodof claim 14, changing the bypass switch from the on state to the offstate includes moving a moveable armature of an electromagnetic relayfrom a closed state to an open state by a spring coupled to the movablearmature.
 16. The method of claim 15, wherein the bypass switch furtherincludes a coil having a voltage rating and wherein the spring isconstructed to hold the moveable armature in the open state against anopposing magnetic field generated by applying a voltage level equal tothe voltage rating to the coil.
 17. The method of claim 11, whereingenerating inverter commands includes generating pulse width modulationcommands.